Method of purifying used oils



Patented Feb. 3, 1942 METHOD OF PURIFYING USED OILS Charles M. Ambler, .lr., Jenkintown, Pa., assignor to The Sharples Corporation, Philadelphia, Pa., a corporation of Delaware No Drawing. Application August 9, 1939, Serial No. 289,322

9 Claims.

impurities of an acid nature produced as a result of oxidation of th oil in service. The invention is applicable to the purification of many types of hydrocarbon oils whose utility has been impaired incident to use; e. g., used car journal oil, oil

which has been used as a lubricant in internal combustion engines, dielectric oil, etc.

In the reclamation of oils of the types mentioned above, it has been quite common to treat the oil with an aqueous alkaline reagent to effect coagulation of the carbonaceous and inorganic matter, and neutralization of acidic impurities, the aqueous phase and insoluble impurities being thereafter removed from the treated oil by centrifugation or gravity settling.

An object of the present invention has been to facilitate the reclamation of oils of any of the above-mentioned types, and to effect a more thorough removal of undesired impurities than has heretofore been economically possible. Many used oils contain between 1 and 10% of insoluble impurities, and the removal of such impurities to a sufficient degree to condition the oil for re-use presents a serious problem. By the practice of the present invention, the removal of these impurities is eificiently achieved.

A second object of the invention has been to effect a removal of impurities by centrifugal force in conjunction with a treatment involving accumulation withinthe centrifugal rotor of a much smaller quantity of bowl cake than has been present in cases in which corresponding oils are treated by prior art processes.

The invention rests upon the discovery that,

when an aqueous alkaline reagent is added to a used hydrocarbon oil containing impurities such as those mentioned above, and a part of the water of dilution of the aqueous reagent is thereafter removed from the mixture by evaporation,

changes occur which make it possible to separate 5 ill to effect agglomeration of insoluble impurities. This reagent may be any of the reagents known to the used oil reclamation art for the accomplishment of such agglomeration. It may, for example, be an aqueous solution of sodium carbonate, trisodium phosphate, sodium'hydro-xide, tri-ethanol amine, or any other reagent or mixture of reagents capable of eifectingthe desired result. The preferred reagent for use in the process is sodium silicate, The use of this reagent in the art of used oil reclamation is already well known, but surprising advantages are achieved in connection with the use thereof in accordance with the present invention, as compared with prior art methods. 1

The reagent is first finely dispersed in the oil by intense agitation, which may be accomplished by a high speed mechanical mxier, or by any other suitable form of mixing-device capable of accomplishing extremely fine dispersion of the reagent in the oil. a

The mixture of oil and reagent is next heated to remove a substantial proportion of the water contained in the'aqueous reagent, and to concentrate the reagent while it is still finely dispersed 'in the oil. In case the reagent used is a sodium silicate solution, this concentrating operation is preferably continued until the ratio of Water contained in the mixture to sodium silicate (on a dry basis), which may be designated by the formula X(Na2O').Y(SiO2), is not greater than 9:1, and

best results are attained when this ratio is not greater than 7:1. Regardless of the extent to which the concentrating operation is carried, however, it has a beneficial eifect on the efficiency of the ensuing separating step. The concentrating operation may be performed at a temperatur in excess of the boiling point of water under atmospheric pressure, or it may be performed at a temperature below the atmospheric boiling point of water, with the aid of vacuum. In the preferred embodiment of the invention, the reagent is concentrated by evaporation until practically all of the water content of the mixture is removed.

The mixture of oil, impurities, and reagent which has been at least partially dehydrated, is next passed to a centrifugal separator, where a separation of the oil from the reagent and impurities takes place.

. Regardless of the exact degree of concentration achieved, and regardless of the nature of the alkaline agglomerating reagent, it will be found that the step of concentrating the aqueous reagent after addition to the oil results in an improvement in the efficiency of the ensuing step of centrifugal separation. While I do not wish to be bound by any theory as to the reasons for the achievement of this advantage, I believe that it can be at least partially explained on the following basis.

An aqueous alkaline reagent can be dispersed more finely in an oil provided the reagent is relatively dilute, than if it is more concentrated. On the other hand, certain of the advantageous effects in conditioning the material for centrifugation attained by the use of the reagent are probably more efiiciently accomplished under conditions of high reagent concentration than with low reagent concentration. Thus, while high reagent concentration affords certain advantages, it affords the incidental disadvantage of inadequate or difiicult mixing, in cases in which the reagent is of high concentration when initially introduced.

In the practice of the present invention, fine disperson of the reagent in the oil is achieved by introducing it in relatively low concentration, and the reagent is concentrated only after such dispersion exists. By the practice of the invention,

the advantages of high reagent concentration are thus attained Without the incidental disadvantage of inadequate dispersion which would otherwise be entailed in this connection.

The practice of the invention may be either continuous, or by batch operation. In case the a process is made continuous, it will be desirable to use suitable proportioning apparatus, such as that described and claimed in the patent to Jones No. 2,009,890, to effect accurate proportioning of the reagent to the oil, into which it is continuously introduced. The oil and reagent may then be intensely mixed in any suitable form of mixing device during continued flow, and then passed to a flash evaporating chamber, which is maintained under vacuum in order to cause continuous evaporation of water during continuous flow of the mixture through the evaporating chamber. The mixture flowing from the evaporating chamber will then be passed directly to a centrifugal separator to'effect the final step of separating the reagent and impurities from the oil.

The step of removing at least a substantial part of the water contained in the oil after mixing with the alkaline solution converts a large part of the impurities in the oil into a condition in which they may be removed by simple gravity subsidence. The invention may therefore be practiced by a sequence of steps involving treatment of the oil with alkali as suggested above, then separating a part of the impurities in the oil therefrom by gravity settling, and finally passing the partially purified oil to a centrifugal separator to effect removal of residual impurities therefrom. This sequence of steps may be followed in connection with continuous or batch operation.

In an example of the practice of the invention, 100 gallons of used car journal oil were first thoroughly mixed with a sodium silicate solution containing 2.5 gallons of brand sodium silicate, manufactured by the Philadelphia Quartz Company, in 22.5 gallons of water. After the reagent was thoroughly mixed with the oil, the mixture was heated to a temperature of 300 F. until practically all of the water had been evaporated therefrom. The dehydrated mixture was then passed to a centrifugal separator, from which the oil was continuously discharged, and

in which the impurities removed from the oil were retained as a bowl cake, during centrifugation. Both the efficiency of the centrifugal separating step in producing a purified oil, and the quantity of bowl cake deposited, were materially reduced as compared to operations in which the same oil was treated with the same reagent without performance of the intermediate evaporating step between mixing and centrifugation.

Modifications will be obvious to those skilled in the art, and I do not therefore wish to be limited except by the scope of the subjoined claims.

I claim:

1. In the purification of used hydrocarbon oils, the process comprising mixing the oil to be purified with an aqueous alkaline reagent and thereby effecting fine dispersion of the alkaline reagent in the oil, thereafter subjecting the mixture to an evaporating operation to concentrate the reagent by removing a substantially large part of the water contained therein; and finally separating said alkaline reagent and impurities from the oil by subsidence.

2. In the purification of used hydrocarbon oils, the process comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby effecting fine dispersion of the sodium silicate solution in the oil, thereafter subjecting the mixture to an evaporating operation to concentrate the sodium silicate solution by removing a substantially large part of the water contained therein, and finally separating said sodium silicate and impurities from the oil by centrifugal force.

3. In the purification of used hydrocarbon oils, the process comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby effecting fine dispersion of the sodium silicate solution in the oil, thereafter subjecting the mixture to an evaporating operation to concentrate the sodium silicate solution by removing a substantially large part of the water contained therein, until the water content of the mixture has been reduced to a ratio of water to sodium silicate in the mixture of not greater than 9:1, and finally separating said sodium silicate and impurities from the oil by centrifugal orce.

4. In the purification of used hydrocarbon oils, the process comprising mixing the oil to be purified with an aqueous alkaline reagent and thereby efiecting fine dispersion of the alkaline reagent in the oil, thereafter subjecting the mixture to an evaporating operation to eifect substantially complete dehydration thereof, and finally separatingsaid alkaline reagent and impurities from the oil by subsidence.

5. In the purification of used hydrocarbon oils, the process comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby effecting fine dispersion of said sodium silicate solution in the oil, thereafter subjecting the mixture to an evaporating operation to effect substantially complete dehydration thereof and finally separating said sodium silicate and impurities from the oil by centrifugal force.

6. In the purification of used car journal oil, the process comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby effecting fine dispersion of the sodium silicate solution in the oil, thereafter subjecting the mixture to an evaporating operation to concentrate the sodium silicate solution by removing a substantially large part of the Water contained therein, and finally separating said sodium silicate and impurities from the oil by centrifugal force.

7. In the purification of used car journal oil, the process comprising mixing the oil to be purified with an aqueous alkaline reagent and thereby effecting fine dispersion of the alkaline reagent in the oil, thereafter subjecting the mixture to an evaporating operation to effect substantially complete dehydration thereof, and finally separating said alkaline reagent and impurities from the oil by centrifugal force.

8. In the purification of used hydrocarbon oils, the steps comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby efiecting fine dispersion of the sodium silicate solution in the oil, thereafter subjecting the mixtur to an evaporating operation to concentrate the sodium silicate solution by removing a substantially large part of the water contained therein, and thereafter separating impurities from the oil by subsidence.

9. In the purification of used hydrocarbon oils, the steps comprising mixing the oil to be purified with an aqueous solution of sodium silicate and thereby efiecting fine dispersion of the sodium silicate solution in the oil, thereafter subjecting the mixture to an evaporating operation to remove substantially all of the water contained therein, and thereafter separating impurities from the oil by subsidence.

CHARLES M. AMBLER, JR. 

